In the manufacture and processing of various semiconductor devices, wire bonding machines are often used to provide interconnections between components in the devices. The interconnections are typically provided in the form of a wire loop that is “bonded” between a first bonding location (e.g., a die pad of a semiconductor die) and a second bonding location (e.g., a conductive region of a substrate such as a lead of a leadframe). Such wire bonding machines typically include a wire feed system for feeding a wire on a wire spool to a bond head of the wire bonding machine. The bond head of the wire bonding machine typically carries a wire clamp, a transducer (e.g., an ultrasonic transducer) and a bonding tool (e.g., a capillary tool, a wedge tool, etc.), amongst other components.
The wire bonding machines provide for motion of the bonding tool (e.g., through the motion of the bond head) in order to form a wire loop of a desired shape. During motion of the bonding tool (e.g., while shaping the wire loop) the wire clamp is operated between an “open” and a “closed” position such that wire may be fed from a wire spool through the wire clamp when the wire clamp is open, but additional wire is not fed from the wire spool when the wire clamp is closed. The wire length that is fed past the wire clamp during the looping motions (i.e., when the wire clamp is open) is often termed the wire “payout.”
It would be very desirable to know the wire payout provided by looping motions of a wire loop, because the wire payout will affect the ultimate shape of the wire loop. Conventionally, if desired, the wire payout has been calculated using offline manual measurements taken after the wire loop is formed. Such calculations tend to be inaccurate and time consuming. Problems arise because of the lack of accurate and timely measurements of wire payout. For example, process variables (e.g., the bonding tool used, tension provided by the wire feed system, amongst others) affect how much payout is provided in a given wire loop. When these variables change (e.g., on the same or different wire bonder platform) the wire payout also changes. Thus, inconsistent wire loops may undesirably result.
Thus, it would be desirable to provide techniques for measuring and/or calibrating wire payout, and to use the wire payout in conjunction with wire bonding operations.